git merge

The git merge tool is used to merge one or more branches into the branch you have checked out. It will then advance the current branch to the result of the merge.

The git merge command was first introduced in Basic Branching. Though it is used in various places in the book, there are very few variations of the merge command — generally just git merge <branch> with the name of the single branch you want to merge in.

We covered how to do a squashed merge (where Git merges the work but pretends like it’s just a new commit without recording the history of the branch you’re merging in) at the very end of Forked Public Project.

We went over a lot about the merge process and command, including the -Xignore-all-whitespace command and the --abort flag to abort a problem merge in Advanced Merging.

We learned how to verify signatures before merging if your project is using GPG signing in Signing Commits.

git log

The git log command is used to show the reachable recorded history of a project from the most recent commit snapshot backwards. By default it will only show the history of the branch you’re currently on, but can be given different or even multiple heads or branches from which to traverse. It is also often used to show differences between two or more branches at the commit level.

This command is used in nearly every chapter of the book to demonstrate the history of a project.

We introduce the command and cover it in some depth in Viewing the Commit History. There we look at the -p and --stat option to get an idea of what was introduced in each commit and the --pretty and --oneline options to view the history more concisely, along with some simple date and author filtering options.

In Creating a New Branch we use it with the --decorate option to easily visualize where our branch pointers are located and we also use the --graph option to see what divergent histories look like.

In Private Small Team and Commit Ranges we cover the branchA..branchB syntax to use the git log command to see what commits are unique to a branch relative to another branch. In Commit Ranges we go through this fairly extensively.

In Merge Log and Triple Dot we cover using the branchA...branchB format and the --left-right syntax to see what is in one branch or the other but not in both. In Merge Log we also look at how to use the --merge option to help with merge conflict debugging as well as using the --cc option to look at merge commit conflicts in your history.

In [_git_notes] we use the --notes= option to display notes inline in the log output, and in RefLog Shortnames we use the -g option to view the Git reflog through this tool instead of doing branch traversal.

In Searching we look at using the -S and -L options to do fairly sophisticated searches for something that happened historically in the code such as seeing the history of a function.

In Signing Commits we see how to use --show-signature to add a validation string to each commit in the git log output based on if it was validly signed or not.

git stash

The git stash command is used to temporarily store uncomitted work in order to clean out your working directory without having to commit unfinished work on a branch.